This invention relates to tie straps and associated rivets used in saw chains. It pertains particularly to a method of making these tie straps and rivets as an integrated assembly.
Saw chains, in general, comprise alternating right hand and left hand cutters separated by blank links. The cutters and blank links are fastened to one another by rivets with concentric shoulders providing separation between opposed tie straps or tie straps and cutters. This allows the elements to rotate at the riveted joints. The blank links comprise paired opposed tie straps joined by rivets. The cutters are opposed by tie straps and joined by the rivets.
In the past, separate rivets and concentric shoulders have been hand assembled, inserted into the tie straps and cutters, and the rivets spun to form heads. Presently the assembly is done by machine, but due to the small size of the parts, automation is difficult.
In order to facilitate automated assembly and reduce the cost of the chains, the holes in the cutters and tie straps into which the rivets are installed are made considerably larger than the rivets. The resulting chain is therefore not dimensionally uniform and is loose fitting even when new. Accordingly, the general object of the present invention is to provide tie straps and rivets for saw chains in an integrated assembly.
It is a further object of the present invention to provide such integrated assemblies wherein concentric shoulders are formed into the rivets to thereby achieve with a single element the features of a tie strap, a rivet for attaching same to an opposite tie strap, and an intermediate shoulder that spaces the tie straps and provides a bearing surface for free pivoting of the intermediate center link.
It is a further object of the present invention to provide a method wherein the assembly is formed in one piece without any hand installation of parts.
It is a further object of the present invention to provide such a method wherein the assembly is precision formed having uniform rivet spacing for accurate alignment on the saw chain.
It is a further object of the present invention to provide such a method which is capable of mass producing the assemblies at a low cost.
It is a further object of the present invention to provide such a method wherein the tie straps are formed with medial cutouts and inwardly angled edges on each side, and thus can be used for either right hand or left hand application.